1. Field
The present disclosure generally relates to methods and equipment for laying up composite parts using automated fiber placement, and deals more particularly with a method and device for compacting fiber tows, particularly fiber tows having angular fiber orientations.
2. Background
Automated fiber placement (AFP) machines are used in various industries to layup composite parts, particularly small parts and/or those having complex geometries, to increase rate and precision. AFP machines place a bandwidth of fiber tows on a layup tool such as a mold tool or layup mandrel. The fiber tows may be in the form of split tape, and may comprise thermoset or thermoplastic pre-impregnated unidirectional fiber reinforcements that are laid up in various fiber orientations e.g., 0°, +/−45°, +/−60°, 90°. A bandwidth of the tows are dispensed, cut to length and compacted onto the tool by an AFP head that is typically automatically controlled by a numerically controlled robot or similar manipulator. The incoming fiber tows are often heated to increase their tack before being fed beneath a single compaction roller that both applies and consolidates and/or debulks the entire bandwidth of tows onto the layup tool as the AFP head moves over the tool surface.
Difficulties may be encountered when laying up fiber tows along a path forming an angle relative to an edge on the tool. For example, when laying up fiber tows with +45 or −45° orientations over two tool surfaces intersecting to form a right angle edge, such as a horizontal surface and the vertical surface, there is a resultant area of non-compaction as the roller transitions over the right angle edge and must lift off of the horizontal surface in order to rotate the full bandwidth of tows onto the vertical surface. In the past, this problem has been addressed by making additional passes with the AFP machine over the non-compacted areas, however this approach increases the layup time and associated costs. Another problem associated with using a single compaction roller is the need for laying up additional tow material on the vertical surface in those part applications where an edge of the part falls below a minimum layup distance beyond the area of non-compaction.
Accordingly, there is a need for a method and compaction device for use with AFP machines that reduces the non-compaction area caused by the compaction roller lifting off of the tool surface as it transitions over high angle features. There is also a need for a method and compaction device of the type mentioned above which reduces the need for laying up additional tow material where the edge of the part falls under a minimum layup distance beyond an area of non-compaction.